This matchup is a solid 2/8. If Kirby loses the lead at ANY moment, he automatically loses the entire game. Sonic can just run away and Kirby is too slow both on the ground and in the air to catch him, and Final Cutter is borderline useless as a projectile since Sonic will mostly be in the air. At least Jigglypuff has good air speed and a fine nair to go for it. If by some miracle Kirby gets the lead, it's way more difficult for him to keep it since Sonic is faster, combos him better, and can safely go pretty much anywhere Kirby can. As mentioned above, probably the only thing that keeps this matchup from being borderline unwinnable is that Kirby's jab infinite has more priority than both Spin Charge and Spin Dash, but Sonic has rather obvious ways around those. Put simply, this is up there with Ganondorf vs. Pikachu as one of the most one-sided matchups in the game.